The invention relates to regenerative turbine pumps which are sometimes also referred to as turbine pumps, periphery pumps, turbulence pumps, or friction pumps. The turbine pump name has been used because (a) the impeller is rotated at high speed and (b) has a plurality of vanes, resembling those of a steam turbine, machined into the periphery of the impeller. Some such pumps have vanes on only one side of the impeller, although, the more common form has vanes on both sides of the impeller. Most, but not all, have radial vanes. Others have no-radial vanes. Some forms of regenerative turbine pumps may be multistage structures. Two stage regenerative turbine pumps direct a fluid from a first stage to a second stage. While the invention will be described in terms of the type having vanes on both sides of the impeller and a single stage pump it will be understood by those skilled in the art that the invention has application to other regenerative pump forms.
Regenerative turbine pumps will move a relatively low flow of fluid at a relatively high head. More specifically, such pumps have a relatively steep head capacity curve. The regenerative turbine pump has higher efficiencies at low flows than a centrifugal pump. A regenerative turbine type pump typically will produce several times the pressure produced by a centrifugal pump having an impeller of equal diameter and operating at the same speed.
Regenerative turbine pumps have many applications where high head and low flow are required. Typical applications include: boiler water feed systems, rocket booster systems, car wash applications, chemical feed systems, chlorine injection systems, condensate return systems, dry cleaning systems, electronic cooling systems, high pressure sprays, petroleum refining processes, TV tube/CRT manufacturing, as well as air conditioning, refrigeration, and heating applications.
The most important application of regenerative turbine pumps is for boiler feed systems. The addition of feed water to a boiler is handled by two general methods: intermittent (on-off) operation and continuous operation. In a continuous operation, the feed water is controlled by a modulating valve that regulates to keep a constant water level in a boiler. Depending on the flow requirement, the pump can operate at any point along its performance curve. During the operating cycle of a boiler it is normal for the boiler periodically become full so that there is no demand for more water. At such times a modulating valve will nearly close and the pump will flow only a very small amount of by-pass water.
A standard regenerative turbine impeller has radial vanes which have a uniform height. The advantages of this kind of impeller include a low manufacturing cost and a steep head capacity curve which provides stable operation at substantially fixed flow and pressure conditions. A disadvantage of the conventional impeller is that it is not suitable for continuous variable flow operation.
Unlike a centrifugal pump, a regenerative turbine pump has an increasing horsepower requirement with decreasing flow. Accordingly, the horsepower consumption near shut-off conditions is much higher than that at the best efficiency point. The steeper the head capacity curve, the larger the horsepower variation at different flows. For continuous operation applications, the motor size is chosen based on the power consumption at the smallest operating flow. Thus, from the view point of saving energy as well as using motors with smaller horsepower, flat head-capacity curves are preferred for regenerative turbine pumps used in variable flow applications. Therefore, standard impellers with steep head-capacity curves are not suitable for continuous operation.
It is an object of the invention to provide a construction that will require less power to operate at variable flow conditions.
It is an object of the invention to provide such apparatus having a relatively flat head capacity curve.
It is another object of the invention to provide an apparatus having a novel impeller.
Still another object of the invention is to provide apparatus that will be inexpensive to manufacture.